Interstitial lung disease (ILD) is a major complication and the leading cause of mortality in scleroderma (SSc, systemic sclerosis). In addition, patients of African ancestry suffer from higher morbidity and mortality rates. The etiology of SSc, including the reasons underlying the wide variation in disease progression and severity remain unknown. For these reasons, it is important to understand the mechanisms through which SSc-ILD develops that may explain the racial differences in SSc-ILD outcomes. The low concordance rate between monozygotic twins suggests an important role for epigenetic or environmental factors in SSc susceptibility. Since it is influenced by the environment, epigenetic variation, inherited both directly and through shared environmental effects, may play an important role in SSc-ILD risk. Evidence suggests that epigenetic changes play an important role in the development of autoimmunity. These epigenetic markers have the potential to serve as biomarkers for the development and progression of SSc-ILD. The hypothesis of this study is that epigenetic factors are a significant contributor to severity of SSc-ILD in African-American (AA) patients. Its goal is to identify DNA methylation loci as biomarkers of SSc-ILD and its severity, which supports the long-term goal to delineate the role of DNA methylation in SSc risk and severity. This application proposes three specific aims: 1) comprehensive identification of differentially methylated cytosines (DMCs) and regions (DMRs) associated with SSc-ILD and its severity in AAs, 2) test if the most significant DMCs and DMRs are associated with genetic variation, and 3) test if the most significant DMCs and DMRs are associated with gene expression levels. Alveolar macrophages will be isolated from bronchoalveolar lavage on 34 AA SSc-ILD patients and 26 AA controls. Reduced representation bisulfite sequencing will be performed and DMCs and DMRs associated with SSc-ILD and disease severity will be identified. The 5 most significant DMCs/DMRs will be selected for genetic and expression studies. These results have the potential to identify DNA methylation loci as biomarkers of SSc-ILD and disease severity, thus contributing to an increased understanding of the molecular mechanisms of SSc-ILD and ultimately may lead to the development of effective diagnostics, prognostics and therapies.